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Moon in the Middle

StarDate:

September 17, 2017

The crescent Moon starts the week as the centerpiece of a beautiful morning lineup tomorrow. It’s flanked by four pinpoints of light — two above, and two below. The ones below it are a bit tough to find, but the ones above should be easy targets.

The brightest of the Moon’s companions is Venus, the dazzling “morning star.” It rises a few hours before the Sun, so it’s in good view by dawn’s early light.

Although it looks like a star, Venus is really a planet — our closest planetary neighbor. Thanks to the combination of its distance and our viewing angle, it’s at its faintest — it’s only half as bright as it is at its peak. It won’t start brightening until the end of the year.

The true star Regulus stands below Venus. It’s only about one percent as bright as Venus. But it’s one of the night sky’s leading lights, so you won’t have any trouble finding it.

Things get trickier when you look below the Moon. The planet Mercury is to the lower left of the Moon as twilight begins to paint the sky. And it’s pretty bright — only the Moon and Venus outshine it. But it’s so low in the sky, and so immersed in the waxing twilight, that you need a clear horizon to pick it out.

And Mercury has a close companion that’s especially hard to find. Mars is only about a tenth as bright as Mercury, so it’s a tough target. But it lines up between Mercury and the Moon, which can help you find it — the faintest member of a beautiful morning lineup.

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